Question

A vessel contains equal weights of two gases x and y at 8 atm pressure. If the partial pressure of x is 3 atm, then the ratio of molecular weights is:

• A. 3:5
• B. 5:3
• C. 9:25
• D. 25:9

Answer 1

The correct option is B 5:3

According to Dalton's law of partial pressure for non-reacting gases,

$P_{Total}=p_x+p_y\Rightarrow p_y=8-3=5atm$

From ideal gas law, $p\propto n$

$\frac{p_x}{p_y}=\frac{n_x}{n_y}=\frac{M_y}{M_x}$

$\frac{3}{5}=\frac{M_y}{M_x}$

Note- $p_y=5atm$

Thus, $\frac{M_x}{M_y}=5:3$
Option B is correct.